Sudoku Rules
One grid. One rule. Infinite possibilities. Here is everything you need to know about how Sudoku works.
The Grid
A standard Sudoku puzzle consists of a 9×9 grid, which is further divided into nine 3×3 regions called boxes (also known as blocks or regions). When you start a puzzle, some cells are already filled with numbers — these are called givens or clues. Your job is to fill in the remaining empty cells.
The Three Rules of Sudoku
Every ROW must contain the numbers 1 through 9, with no repeats. Each of the nine horizontal lines across the grid must have all nine digits exactly once.
Every COLUMN must contain the numbers 1 through 9, with no repeats. Each of the nine vertical lines down the grid must have all nine digits exactly once.
Every 3×3 BOX must contain the numbers 1 through 9, with no repeats. Each of the nine outlined regions must have all nine digits exactly once.
That Is It — Really
Those three rules are all there is to Sudoku. There is no addition, no subtraction, no complicated math. Every solving technique ever developed is simply a clever way of figuring out which number goes where based on these three constraints. The beauty of Sudoku lies in how such a simple ruleset creates endlessly varied and deeply challenging puzzles.
What Sudoku Is and Is Not
Key Terms to Know
Frequently Asked Questions
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Now You Know the Rules — Time to Play!
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